Plastic container construction



E. R. GOODING v PLASTIC CQNTAINER CONSTRUCTION Aug. 8, 1967 2 Sheets-Sheet 1 Filed July 26, 1965 FIG.1

PIC-3.8

INVENTOR ELWYN R. GOODING A TTORNEVS 2 Sheets-Sheet 2 Filed July 26, 1965 FIG.5

INVENTOR E LWYN R GOODING A 7' TORNEKS United States Patent 3,334,802 PLASTIC CONTAINER CONSTRUCTION Elwyn R. Gooding, Ann Arbor, Mich., assignor to Ex-Cell-O Corporation Filed July 26, 1965, Ser. No. 474,869 1 Claim. (Cl. 229-37) ABSTRACT OF THE DISCLOSURE A container blank for a tubular square cross-section container having a fold-in bottom closure formed from foldable sheet plastic material and provided with thermoformed vertical and horizontal side panel scores formed to a depth sufiicient to provide linear strengthening ribs along the outside junctrires of the formed container panels. The bottom closure portion of the blank is provided with thermo-formed diagonal score lines formed to a depth sufiicient to provide a rib on the inside of the container blank so that the fold-in bottom closure is formed by folding the closure panels toward the groove portion of the diagonal score lines.

The present invention relates to a plastic carton or container for the packaging of relatively heavy products such as milk and other dairy products and more particularly to a novel fold-in bottom closure for such a plastic carton or container.

In the packaging of fluids extensive use has been made of containers formed of paperboard sheet material having an overall coating of thermoplastic film such as polyethylene applied on the surface of the sheet. One form of a container of this type just noted and presently in wide commercial use is disclosed in US. Patent No. 3,120,335, issued Feb. 4, 1964.

Although plastic coated containers of the above described type have been commercially successful, there are certain disadvantages inherent in their use, one of the most serious of which involves the exposure of the raw or cut edges of the paperboard portion of the container bottom to the product. The result is that the product is absorbed by the paperboard causing a penetration or wicking thereof with the resultant weakening of the board and eventual leaking. Another disadvantage of the present paperboard coated container is that continuous vibration during extended transportation can cause a failure of the container bottom by the coating exhibiting fatigued and cracking, thus, allowing the fluid to leak out of the container. The result is that with the existing plastic coated containers various measures such as increasing the number and thickness of the layers of material and blocking or sealing at least a portion of the interior raw edges is necessary to insure a fluid tight container having substantial shelf life and shipping capabilities.

An object of the present invention is the provision of a new and improved container fold-in bottom closure formed of thermoplastic sheet material in which a minimum amount of material is utilized to provide a liquid tight container.

A further object of the invention is the provision of a new and improved container bottom closure formed of thermoplastic sheet material which will be strong, simple to erect, close and seal, and susceptible of high volume economical machine production for packaging liquid products.

3,334,802 Patented Aug. 8, 1967 Still another object is to provide a novel container bottom closure construction having side wall panels together with bottom flaps so arranged that successive blanks may be formed from a continuously moving web of sheet plastic material without any material waste.

It is a further object of the present invention to provide a novel method for forming a container bottom closure from thremoplastic sheet material comprising the steps of, forming a partial pattern of score lines on one side of a sheet of thermoplastic material, forming the remaining portion of the pattern of score lines on the opposite side of the sheet, forming a container bottom from the blank by folding about the score lines so as to always fold toward the groove portion of each of the score lines and heating and pressure sealing the overlapping portions of said closure.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same be comes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIG. 1 is a layout view of a portion of a blank fiom which the bottom closure of the instant invention is for-med showing the outside surface thereof.

FIG. 2 is a fragmentary perspective view of an inverted container showing a bottom end closure erected from the blank of FIG. 1.

FIG. 3 is an outside view of the container bottom of FIG. 2.

FIG. 4 is a section on the line 44 of FIG. 2.

FIGS. 5, 6 and 7 are fragmentary perspective views illustrating sequentially various steps in forming the bottom closure.

FIG. 8 is an enlarged fragmentary sectional view taken along a plane indicated by the lines 88 in FIG. 1.

FIG. 9 is an enlarged fragmentary sectional view taken along a plane indicated by the lines 9-9 in FIG. 1.

FIG. 10 is an elevational bottom view of the container showing one form of heating and sealing pattern in accordance with the invention.

Referring now to the drawings, FIG. 2 generally indicates a thermoplastic container bottom closure made in accordance with the principle of the present invention. The container described in this application is made from high impact polystyrene, but it should be understood that other suitable heat sealable thermoplastic sheet material may be employe such as polyethylene, for example, without departing from the spirit and scope of the invention.

Referring more specifically to FIG. 1, the container bottom is shown as a fragmentary blank 10 with a pattern of appropriate score lines and having the outside surface of the blank showing. The bottom closure layout of FIG. '1 is adapted to be erected into the completed container closure of FIG. 2. The container includes a tubular body 12 which in the present instance is of substantially square cross-section. One end of the body 12 is provided with a suitable end closure (not shown) such as the familiar gable top end closure of previously mentioned Patent No. 3,120,335 the details of which are of no concern here.

The flat bottom closure 14 is shaped from the blank of FIG. 1 which is separated into two groups of panels by staggered score line 16. The material above score line 16 is the flat bottom closure While the portion below the score line 16 is the body and comprises four panels 17-29 and side seam flap 21. The body group is defined moved toward movement, members 39 seen in FIG. 8, for example, done so that all the score lines on'the 3 on the sides by edges 22 and 23 with the panels being separated by score lines 24-27. The material above the score line 16 is referred to as the bottom closure group and comprises major bottom closure panels 28 and 30, minor bottom closure panels 29 and 31, and extension 32 of the side seam flap 21.

It should be noted that the transverse score line 16 is notcontinuous but is formed in staggered portions interrupted by the perpendicular score lines 24-27. The purpose of this staggered scoring is to accommodate the thickness of the sheet material as it is bent along the score lines when the closure is erected and thus prevent crowding of the material at the various corner junctions of the score lines. This not only enhances the strength and appearance of the finished container but facilitates its erection and closure by automatic machinery. It should also be noted that the score line 16 could be extended to provide a score line between flaps 32 and 21.

As can be seen in FIG. 1 the alternate side panels 17, 19 have respectively connected therewith opposed rectangular bottom closure panels 28, 30. The latter which form extensions of panels 17, 19 respectively are connected to the minor closure flaps 29, 31 along hinge score lines 33, 34 and 35 and are extensions of the body score lines 24, 25 and 26. Panel 31 is joined to flap 32 by hinge score line 36 which is an extension of score line 27. Each of the panels 29, 31 are divided by a pair of diagonal score lines 37, 38 into two 45 degree right triangular panels 39, 40 and a trapezoidal panel 41.

The major closure panels 28, 30 are equal in their width dimension indicated at A (FIG. 1) when measured from score line 16 to their respective free edges 42, 43.

The distance A exceeds one-half the width dimensions W e of panels 18-20, by the amounttindicated by C (FIG. 3)

to provide for the required overlap. The minor closure panels 29, 31 are equal in their width dimension indicated at B, when measured from score line 16 the respective free edges 44, 45. The distance B should be approximately one-sixth of the width W to achieve a machine foldable and sealable closure as will be hereinafter explained.

To construct the container bottom closure as shown in FIG. 2, a flat side seamed blank is formed by folding the blank upon itself and sealing the side seams flap 21 and its extension 32'to the inside faces of panels 17 and 28 by using any of the well-known plastic sealing methods such as heat, sound or light. Following the tubing of the container body on a mandrel (not shown) with the bottom closure panels extending outwardly from the face of the mandrel, the container bottom will be infolded and sealed in the manner illustrated in FIGS. 5-7 and 10.

As seen inFIG. 6, the major panels 28 and 30 are each other. This causes the triangular panels 39 to rotate around score lines 33 and 36 so that the inside surfaces of panels 39 and panel 28 are coming together. At the same time and during the same are rotating around score lines 37, thus the outside surfaces of panels 39 and 41 are coming together (FIG. 6); Triangular panels 40 make the same movements as panels 39 with major panel 30 and portions of trapezoidal panels 41.

In order to attain a successful machine folding closure using the minimal amount of plastic material specified hereinbefore by dimensions A, B and C, it is essential that the score lines he formed so that the plastic will be folded toward the groove portion of the score line. As the scoring of the blank is container body and closure, with the exception of diagonal score lines 37 and 38, are formed with the rib portion toward the outer face of the blank and a groove opposite thereto. In the case of the diagonal scores, represented by line 37 in FIG. 9, the rib portion is on the inner face of the blank so that the adjacent panels 39 and 41 will also fold toward the groove. By this scoring method, it is possible to infold the panels 41 without requiring contact thereon of machine folding contact and movement of major panels 28 and 30 by the forming and sealing machine elements.

A further advantage of applicants closure design is that the panels may be folded ment having an H-shaped design indicated at 46 in FIG. 10. While various forms of heat sealing methods can be employed, such as heat bars and radiant sealers, it has been found that impulse sealers employing water or air cooling means are the most satisfactory. By this method,

a controlled amount of heat can be appliedtogether with a static force to cause the plastic material to flow in the regions of contact with the heating elements.

It will be noted in FIG. 10 that the heating pattern 46 consists of dual line contact areas arranged to overlie the free edges 42, 43, 44 and 45 of the center and side joints.

rial at the score while permitting the surface of the panels 3 to be sealed to lie in face-to-face contact throughout. The subsequent electrical impulse applied to the heating ribbons While in contact with the fold-in panels followed by pressure will provide a liquid-tight seal for the container. 7 t

At least two methods can be employed in forming the score lines in the sheet plastic. A pressure forming operation of the type wherein male and female blanking dies are used has proved satisfactory for a polystyrene sheet plastic having a thickness in the range of 10 to 30'mils. Applicant has also utilized the method of thermoforming the score lines in the plastic. Thermoformed score lines have the advantage of stress relieving the plastic material which allows for the use of deeper scoring without the,

danger of cracking of the formed container at the scores.

A further advantage of the deeper thermoformed scores results in having pronounced ribs extending along the vertical and horizontal edges of the container. These ribs provide additional strength to the container panels.

to resist both vertical and horizontal forces. It is thus possible to reduce the thickness of the plastic material by using a thermoformed scoring operation, thereby achieving a further saving in the amount of plastic material required for each container.

While it will be apparent that the preferred embodiment of the invention herein disclosed is well calculated to fulfill the object above stated, it will be appreciated that the invention is susceptible to modification, variations and changes without departing from the proper scope and fair meaning of the subjoined claim.

I claim:

A blank for a tubular container having square crosssection and formed of foldable sheet plastic material, said blank comprising in combination:

(a) a top closure group, a fold-in bottom closure group.

and a side wall panel group,

(b) a horizontal score line dividing said bottom closure group from said wall panel group, said horizontal score line extending for the full length of said blank,

(c) four vertical score lines dividing said side wall panel group into four side wall panels and a side seam flap, said vertical score lines being substantially perpendicular to said horizontal score line and extending the full height of said blank,

(d) said four side, panel score lines dividing said bottom closure group into first and second pairs of major and minor bottom closure rectangular panels alternately connected to said wall panels as extensions thereof, a

and pressure sealed by an ele- (c) said vertical score lines and said horizontal score line being thermoformed to a depth suflicient to provide ribs on the outside of the blank wherein the tubular container formed from said blank has pronounced strengthening linear ribs extending along the outside junctures of the container panels,

(f) each of said minor panels being divided by diagonal score lines extending from the two corners which are adjacent to its associated side panels and side seam flap whereby each minor panel consists of a central trapezoidal panel and two right triangular fold-back panels, and

(g) said diagonal score lines being thermoformed to a depth suflicient to provide ribs on the inside of the blank wherein said fold-in bottom closure is formed by folding the closure panels toward the groove portion of said diagonal score lines permitting the surface of the bottom closure panels to lie in face-toface contact throughout.

References Cited UNITED STATES PATENTS Moore.

Casler 22917 Eaton.

Kauifeld 229-37 Egleston et a1. 22917 Bromley 2293.5 Moore 22937 Bostrom 2292.5

Canada.

JOSEPH R. LECLAlR, Primary Examiner.

D. T. MOORHEAD, Assistant Examiner. 

